Trouble at Cabin Branch

[Climax1880]

Hey folks:
I need some confirmation on a problem that I'm having with rock castings. This AM, I began making cast rocks for the South Ridge area on my layout. I mixed up 1 cup of water, 1 cup latex paint and 2 cups of Hydrocal. I sprayed the insides of the molds with "wet" water and poured in the plaster. That was at 10 AM. It is now 4:00 PM and I just flushed out the last mold. The stuff NEVER set. It was as wet when it came out as it was when it went in!!!

My conclusion is that the Hydrocal was TOOOO old. I bought it at the train shop in Spencer, NC and I know that I haven't been in that place for 3-4 years.

Let me know if you think something else could be the problem.

Thanks

JR

 

[jon-monon]

Wonder if hte paint could be part of the problem

 

[DanishKnight]

Originally posted by Climax1880
I mixed up 1 cup of water, 1 cup latex paint and 2 cups of Hydrocal.

I agree with Jon, that the addition of paint is the problem. Have you tried just the paint with the hydrocal? May need to add a little water, but not the full cup. Try a small batch first, like cutting the proportions in half or even a fourth. See how it comes out, then add water if too hard or cures too fast. Then do the full mix.

But then...every time I try things like this I end up wasting way more than I eventually use doing it the recommended way.

Good luck!

 

[DanishKnight]

An after thought! (I have a lot of after thoughts! I've given up hoping I would learn to think things through before I jump, but it ain't happened yet, and I'm running out of time!)

If the normal ratio is 1:2 (1 part water, 2 parts hydrocal), and the purpose of the paint is to add color, first try less paint, a little water, the total of these liquids equalling the total water content, then adjust water/paint volume until you get the results you are looking for.

If none of this makes sense, just ignore everything I say and it should turn out fine the next time! :thumb:

 

[RailRon]

I think that the latex paint is the culprit. Since it contains some organic compounds, it will probably slow down stting time of any plaster-like substance. (You can also retard plaster setting time by adding other organic stuff, e.g. some vinegar...)

IMHO 1/4 of the mixture is too much of that stuff. I would recommend to cast the rocks without any latex color (just Hydrocal plus water) and then color the rocks with several washes of paint.

OR you could add some dry pigment powder (like dark umber) to the Hydrocal before adding water. This stuff hardly affects setting time, and you don't have glaring white spots when you chip off some rock later.

Pigment powders are sold as so called 'Earth paints', and they are dirt cheap. (That's because they ARE dried and powdered dirt! )

Ron

 

[Climax1880]

Hey guys:
Think I solved the problem. TOOOO much liquid and I think that the Hydrocal is running out of shelf life.

Last night I tried just plain water and Hydrocal. It was a 3-1 mix. Boy, does that make a difference. Today we go for coloring the rock castings as I hate to paint over those nasty chipped places too.

Thanks for all your help.

Have a good day all

JR

 

[jon-monon]

Like Ron said pigment will probably work a lot better. If you have to use latex, try a very small amount of very dark paint, instead of a lot of properly colored paint. If you can't get ahold of some pigment today, maybe rit dye, or even food color (would red-blue-green food dye in equal amounts make the yuck brown we all desire?)

 

[Secret Weapon]

Hey,
When I make rocks,I only use a small amount of paint to give it color.Also to hide any chips.1 cup of paint ='s at least 1 more cup of hdyrocal.Mike

 

[neilmunck]

They hydrocal powder will eventually go off though.

Air gets into the bag and brings moisture with it. This reacts with the hydrocal. Eventually so much of the hydrocal will have reacted that the rock castings will be brittle and friable.

You can't do anything about it other than close the bag as tightly as possible and expel all the air to slow the process.